The present invention relates to an electric-current sensing device, a load driving system, and a method for manufacturing the electric-current sensing device and, for example, it relates to an electric-sensing device, a load driving system, and a method for manufacturing the electric-current sensing device, which is suitable for detecting an electric current with high accuracy.
For example, in the load driving system which drives loads such as a motor etc. of an automobile, there is provided an electric power converting device (inverter) which converts an electric power supplied by a power supply source from a direct current to an alternating current by a PWM (pulse width modulation) control. Through a switching operation of a power transistor such as an IGBT (Insulated Gate Bipolar Transistor), the inverter converts the direct-current power supplied by the power supply source to a pulse signal. Then, the inverter generates an alternating-current signal of amplitude and a frequency corresponding to a pulse-width of the pulse signal.
In this regard, when a large current flows, the power transistor such as the IGBT may generate heat exceeding a tolerance. The over-heat of the power transistor causes characteristic variation and lifetime reduction of the power transistor itself. Therefore, detecting an over-current flowing through the power transistor and protecting the power transistor from overheating is requested.
A solution for such a request is disclosed, for example, in Patent Document 1. A semiconductor device disclosed in Patent Document 1 includes: a main IGBT and a sense IGBT through which an electric current smaller than an electric current flowing through the main IGBT flows, where the electric current flowing through the main IGBT is detected by detecting the electric current which flows through the sense IGBT.